The present invention broadly relates to organic desiccation and, more specifically, pertains to a new and improved method and apparatus for drying a moist material, especially an agricultural product.
Generally speaking, the method of the present invention is for drying a moist material by means of air heated by the condenser of a heat pump and subsequently blown through the material being dried by a blower.
In other words, the method of the present invention comprises the steps of inducting fresh air from the ambient natural atmosphere; conducting the inducted fresh air through a condenser of an air-to-air heat pump for heating the fresh air; blowing the heated fresh air through a bin or drying chamber containing the moist material for drying the moist material; and conducting a first portion of exhaust air exiting from the bin or drying chamber containing the moist material through an evaporator of the air-to-air heat pump for recuperating thermal energy.
The apparatus of the present invention comprises a bin or drying chamber for accommodating the material to be dried; an induction duct communicating with the ambient natural atmosphere and with the bin or drying chamber; a blower disposed within the induction duct for conducting fresh air into the bin or drying chamber; an exhaust duct for exhausting used or exhaust air from the bin and communicating with the ambient natural atmosphere and with an upper region of the bin or drying chamber and having an end adjacent the ambient natural atmosphere; an air-to-air heat pump having a condenser and an evaporator; and the condenser being arranged within the induction duct.
In other words, the apparatus of the present invention comprises at least one drying chamber for accommodating the material to be dried and having an inlet end for drying air and an outlet end for exhaust air; an induction duct for the drying air communicating with the ambient natural atmosphere and with the inlet end of the at least one drying chamber; a blower cooperating with the induction duct for inducting the drying air from the ambient natural atmosphere and blowing the drying air into the inlet end of the at least one drying chamber; an exhaust duct for the exhaust air communicating with the outlet end of the at least one drying chamber and having an end exposed to the ambient natural atmosphere; an air-to-air heat pump having a condenser and an evaporator; the condenser having an induction side and being arranged within the induction duct; and the evaporator being arranged at the exposed end of the exhaust duct such that exhaust air passing through the evaporator accedes or is discharged to the ambient natural atmosphere.
Methods for drying grass and apparatus for performing such methods are known.
In a known apparatus the moist exhaust air from the material being dried is conducted in a closed circuit into the region of a cold evaporator of a heat pump and there cooled such that a portion of its moisture is extracted as condensate. The cold and now drier air now flows further into the region of a warm condenser of the heat pump and is heated. The warm and dry air coming from the condenser is blown through the material being dried by a fan, usually a conventional ventilating blower, and extracts moisture therefrom. Circulation then begins anew.
Apparatus of this type have the disadvantage that as the ambient temperature rises, for instance in the afternoon, its thermal content cannot be significantly exploited and consequently all energy requirements must be supplied by the heat pump. There is furthermore the danger that ice will form on the evaporator at low ambient temperatures, for instance below 12.degree. C., which reduces the efficiency of the heat pump.